Simple shear test

In the same way a shear test can be simulated. The geometry and the boundary conditions are shown in Fig. 21.5, while Figs. 21.6 and 21.7 show the distribution of the shear strain, the shear stress, the microstructural flux, and the mi-crostructural parameter, respectively. Again, according to different Dirichlet data for ic, both types of boundary layers are generated. The results are qualitatively the same as in the tension test. 

In the present study an extended continuum mechanical model is derived which is able to predict either weak or stiff boundary layers in thin films. As a possible application, the formation of interphases in polymer films is investigated. In this case it was shown [7, 24, 37] that the local stiffness in the polymer depends on the combination of polymer and substrate. 

This size effect can be utilized to determine additional material parameters included in the model. 

In further investigations, the material parameters have to be identified. This requires comprehensive mechanical tests on layers of different thickness. Furthermore, in order to describe the mechanical properties correctly, additional effects such as viscosity and/or plasticity have to be included into the formulation of the theory. 

Christensen (1972). Analogy between micropolar continuum and grid frameworks under initial stress. Int. J. Solids Struct., 8, 327-346. 

---

PP bead foams were subjected to oblique impacts (167), in which the material was compressed and sheared. This strain combination could occur when a cycle helmet hit a road surface. The results were compared with simple shear tests at low strain rates and to uniaxial compressive tests at impact strain rates. The observed shear hardening was greatest when there was no imposed density increase and practically zero when the angle of impact was less than 15 degrees. The shear hardening appeared to be a unique function of the main tensile extension ratio and was a polymer contribution, whereas the volumetric hardening was due to the isothermal compression of the cell gas. Eoam material models for FEA needed to be reformulated to consider the physics of the hardening mechanisms, so their... 

The simple shear test, also shown in Figure 16, was designed in the "chevron configuration to eliminate premature tensile failure at the corner between the leading edge and the central plate. The propellant at these corners will be compressed during most of the test. 

In order to understand the behavior of composite propellants during motor ignition, we conducted a study of the mechanical and ultimate properties of a propellant filled with hydroxy-terminated polybutadiene under imposed hydrostatic pressure. The mechanical response of the propellant was examined by uniaxial tensile and simple shear tests at various temperatures, strain rates, and superimposed pressures from atmospheric pressure to 15 MPa. The experimentally observed ultimate properties were strongly pressure-sensitive. The data were formalized in a specific stress-failure criterion. 

The aim of this work is to provide both experimental information and a corresponding formalization in order to elucidate structural propellant grain safety during ignition. The experimental data were obtained from uniaxial tensile tests and simple shear tests performed with an imposed hydrostatic pressure varying from atmospheric pressure to 15 MPa. It is well established that the materials studied exhibit time-temperature and pressure-sensitive properties. The ultimate properties reported here are formalized in a proposed stress-failure criterion capable of including the pressure effect. 

General methodologies for correcting laboratory triaxial and simple shear test results to in-situ strengths. (From Chaney, R.C. et al.. Toward a unified approach to soil property characterization In situ versus laboratory. In Strength Testing of Marine Sediments Laboratory and In-Situ Measurements, ASTM STP 883, Chaney, R.C., and Demars, K.R., eds., American Society for Testing and Materials, Philadelphia, PA, 425-439,1985. Reprinted with permission from ASTM.)... 

The relationships reported by Ansal and Erken were established through a series of cyclic simple shear testing of normally consolidated kaolinite clay. In this model the pore pressure build-up is expressed as... 

De Alba, P, Seed, H.B., and Chan, C.K. 1976. Sand Liquefaction in Large-scale Simple Shear Tests, Journal of the Geotechnical Engineering Diznsion, ASCE, Vol. 102, No. GT 9, pp. 909-927. 

G Sell C., S. Boni, and S. Shrivastava. 1983. Application of the plane simple shear test for determination of the plastic deformation of solid polymers at large strains. / Materials Sci 18 903-918. 

Liquefaction is one of the most catastrophic earthquake-induced events that impacts infrastructure built on fully saturated loose sands. Using the earthquake engineering experimental facility at Northeastern University, the liquefaction strength of partially saturated sands has been investigated by performing cyclic simple shear tests on prepared specimens. 

Fig. 21.6 Graphical presentation of the mathematical model presenting maximum excess pore pressure ratio (rumax) generated in loose sands based on cyclic simple shear tests...

Second method is shear test (Vane Cone Shear Test, VCST), in-situ cohesion and friction angle are independently measured in half an hour. Figure 8 shows relationship between VCST and tri-axial compression test or simple shear test in several soil samples. Initial torque, which is the torque when vertical load is zero, correlates to cohesion by tri-axial test. Furthermore, trend angle of approximation line by VCST correlates to friction angle. 

Friction angle by triaxual test O Friction angle by simple shear test ... 

Figure 8. Relationship between VCST test and tri-axial strength test or simple shear test (Sasaki 2010).

It should be noted that this model is based on the mechanics of idealised joints and the analysis of some experimental results of simple shear tests. Certain modifications may be necessary when the model is applied in the presence of cracking activity in the RC member since the stress state in the case of crack-induced interfacial debonding situation is different than the stress state assumed in the derivation of this model. 

Dyvik, R., Berre, T, Lacasse, S. and Raadim, B. 1987. Comparison of truly undrained and constant volume direct simple shear tests. Geotechnique 37 (1) 3-10. 

Tang, Y.X., Hanzawa, H. and Yasuhara, K. 1994. Direct shear and direct simple shear test results on a Japanese marine clay. Pre-Failure D ormation of Geomaterials, Vol. 1 (Sapporo), Balkema, Rotterdam 107-112. 

Table 4 Simple shear test results for some of the most used material models...

Mills and Gilchrist [82] studied oblique impacts in PP bead foams, hi these tests, the material was compressed and sheared. This strain combination could occur when a cycle helmet hit a road surface. The results were compared with simple shear tests at low strain rates and with uniaxial com-... 

The effective shear strength can be tested in the laboratory by means of different test procedures such as a the direct shear test, simple shear test and the triaxial test. Normally testing is performed on saturated material. For every test setup, a clear distinction must be made between testing the material under drained or undrained conditions. From this point of view triaxial tests, type CU (Consolidated Undrained) or CD (Consohdated Drained) allow for a better control of the drainage conditions and porewater pressures than for instance shear box tests. For further elaboration on these types of tests, reference is made to textbooks on Soil Mechanics and laboratory testing (Head, 2006). 

Method 3 Laboratory cyclic simple shear tests... 

The CPT is an acceptable test under every methodology for liquefaction assessment. The CPT is a necessary test for any of the advanced methods of liquefaction assessment, particularly when moving into 2D cases of soil structure interaction or if looking to offshore situations. The CPT will even be necessary if taking undisturbed samples for cyclic simple shear testing, both as a means to extrapolate the test data obtained across the area of the site (only a few of these laboratory tests will normally be carried out) as well as provide data to estimate the sample disturbance from in situ to as-tested conditions. For a description of the CPT, see Appendix B-2.3.2. 

Verification of the effectiveness of improvement technique through laboratory tests, such as triax-ial tests, simple shear tests, and torsional shear tests, offers several advantages and disadvantages. One of the merits of these element tests is that by obtaining soil samples before and after improvement, a more direct inspection can be made. In addition, more accurate measurement of stress, strain, and other parameters can be performed, and therefore, a more accurate characterization of the improved soil is possible. 

Liquefaction resistance of in situ plastic soils can be measured directly by laboratory testing on in situ Shelby samples. Sod samples in a cyclic direct simple shear test are normally first crmsol-idated to its pre-crmsoUdatiOTi pressure (the highest historic pressure experienced by the soil or ct p) and then sheared by cycles of Xcyc under (YvO 3nd initial shear stress (Xst) similar to the in situ stresses of the sample. 

Finally, laboratory tests able to measure the dynamic soil properties at high strain levels have been derived from conventional tests by adding cyclic loading capabilities to the testing apparatus. Examples are represented by cyclic triaxial tests with local strain measurements and cyclic simple shear tests. 

---